High-voltage protection.



w. PETERSEN. HIGH VOLTAGE PROTECTION.

APPLICATION FILED SEPT.Z!| 1914.

Patented Sept. 14, 1915.

Fwy $6 IWwwws: Jkvwar A 4 mafia/ze WWL WALDEMAB PETERSEN, OF DARMSTADT,GERMANY.

HIGH-VOLTAGE PROTECTION.

To all whom it may concern:

Be it known that I, WALDEMAR Pnrnnsnn, subject of the German Emperor,and resident at Darmstadt, Grand Duchy of Hesse, German Empire, haveinvented certain new and useful High-Voltage Protection, of which thefollowing is a specification.

Figure 1 shows the arrangement consisting of the combination of achoking coil a and a condenser a commonly employed for protectingtransformers, for example, from excess voltages. This arrangement canparticularly if the mains have a very low resistance to waves V becomethe seat of excess voltages whichendanger the protected apparatus. Thecombination of choking coil and condenser as is known forms a systemcapable of setting up oscillations which in the limited case upon theapproach of a sufiiciently long traveling wave to the protectedapparatus can produce an excess voltage of three times the magnitude.The excess voltage can be still higher if there is a short circuit inthe conductors to the ends of which the protecting device is connectedat such a distance that the natural period of the short circuited lengthof conductor is identical with the natural period of the protectingdevice. This source of danger particularly arising in networks of cablescan be avoided by connecting a resistance 6 to destroy the eflect acrossthe ends of the choking coil a (Fig. 2) in known manner; butaccording-to the invention the magnitude of this resistance must bedesigned in relation to the selfinduction of the choking coil a and thecapacity of the condenser 0, so that the natural oscillation of theprotecting device is strongly 'or altogether suppressed. Apart from anydamping efiect in the oscillatory circuit a c the following is thedifferentialequation of this oscillatory circuit:

(Z 6. 1 (it 1 where i is the instantaneous value of the current flowingthrou h the choking coil a, R is the resistance of b, is induction of aand C the capacity of the condenser c. The system a 0 is deprived of thecapacity to set up oscil- Speciflcation of Letters Patent.

Patented Sept. it, 1915'.

lations as the solution of this differential equation showsif themagniture R of the reslstance b has the value.

For preventing harmful rises in voltage it is not necessary to choosethis critical value, any other higher resistance can be taken whichdamps the natural oscillation to such an extent that in the secondhalf-period of the natural oscillation a certain allowable limit ofvoltage is not exceeded and thus the known resonance phenomena cannotarise.

Bridging across inductances is as already stated in itself a knownprocedure many times published, yet in all these cases the objectforming the basis of the present invention is not pursued.

The insertion of a resistance in parallel has had for its purpose, forexample, the possibility of annulling an approaching wave and themagnitude of the resistance must be chosen in a definite ratio to theresistance to waves of the mains, while in the arrangement forming thesubject-matterof the invention the parallel resistance in the firstplace is determined from the properties of the choking coil of thecondenser.

The most favorable bridging over resistance under some circumstances isso low that a considerable portion of an approaching traveling wavepasses through the resistance and damages the protected parts of theapparatus before the condenser 0 comes into operation. The effectivenessis therefore still further increased if the arrangement illustrated inFig. 3 is shown. In this the resistance b is in fact connected inparallel with a. part of the protecting choking coil a. The portion (1of the choking coil lying in front of the resistance prevents travelingwaves from passing through, at least for a short time. Also, in thisarrangement it is possisistance branching off from the branch Wire andhaving parallel connection to the choke 15 coil intermediate the ends ofthe choke coil whereby a portion of the choke ,coil is interposedbetween the resistance connection and the one end of the line wire.

In testimony, whereof I have signed my 20 name to this specification inthe presence of two subscribing witnesses.

WALDEMAR PETERSEN.

Witnesses: 4

JEAN GRUND, CARL GRUND.

